This invention relates to devices for conditioning air.
Gas-liquid contact pads have long been used in connection with humidification, evaporative cooling of the air in hot dry climates, etc. Such prior pads have often been constructed of multiple layers of slit and expanded media which are bonded or otherwise secured together.
Many prior pads have been utilized satisfactorily in installations where the air flow velocity through the wetted pad, usually by a fan, is from about 200-400 feet per minute. At these relatively low velocities, the size of the open mesh network of webs and baffles in each expanded layer of pad may be quite small, and yet provide a relatively high evaporative efficiency and low resistance to air flow. For example, many prior pads have been provided with a pattern of about 10-47-20, where:
(a) 10 is the number of transverse slits cut per 8" of width of the media before expanding; PA1 (b) 47 is the number of rows of transverse slits cut per 8" of length of the media before expanding; and PA1 (c) 20 is the number of individual expanded cells per 8" of length of media after longitudinal expansion of the slit media.
In addition, these prior pads have been constructed so that each slit and expanded layer is turned around to face in the opposite direction from its directly adjacent layer to provide a series of individual layers wherein the baffles alternately face in opposite directions relative to the air flow and to each other.
Prior pads with layers of the above pattern and baffles orientation have been found to have, in the above indicated range of air velocities, evaporative efficiencies of about 70%-90% and air flow resistances of about 0.10-0.30 inches of water. This has previously been considered to be very adequate in many uses of such pads.
In recent years, air conditioning has become extremely popular and almost a necessity in geographic regions having very high summer temperatures. Air conditioners of the refrigeration type using an air-cooled condenser are very prevalent, but they use a substantial amount of energy. In today's energy conscious world, it has become desirable to increase the efficiency of air conditioners as much as possible. One way to accomplish this is to provide pre-cooling for the air just prior to its passing over the condenser coils of the air conditioner.
It is a known fact that many fans used in forcing air over an air conditioner's condenser coils are not designed to operate against a high resistance. These fans are intended to create an air flow through the unit in the velocity range of about 500-700 feet per minute. It has been found tht when the above-described prior gas-liquid contact pads are positioned at the air intake to the condenser coils for pre-cooling the latter, and with the high air flow velocities used for air conditioning, the evaporative efficiency of such pads tends to drop substantially, and the air flow resistance also increases, as compared to the efficiency and resistance of low air flow installations.
The present invention is based on the discovery of a unique construction of gas-liquid contact pad which has been found to satisfy the requirements for evaporative pre-cooling of condenser coils of an air conditioner in that the best possible evaporative efficiency is obtained with a minimum of air flow resistance. The improvement is expected to be applicable to other pad uses, such as humidification, as well.
In accordance with the inventive concept, a device for conditioning air has a pad formed of a plurality of layers of slit and expanded metal or other suitable media, with the pad having a plurality of groups of layers therewithin. Each layer within a particular group of layers has its baffles oriented to face in the same direction, while each group is turned around to face in the opposite direction from its directly adjacent group so that the baffles of one group face oppositely to the baffles of the next adjacent group. Such a construction is believed to reduce air turbulence as compared to the alternately reversed baffle orientation of each individual layer of the above-described prior pads.
In addition, means are provided to prevent nesting of adjacent layers within each group of layers. Alternate layers within each group are expanded to a slightly different degree so that the various elements making up each layer support the elements of adjacent layers in spaced unnested relationship.
The dimensions of the expanded cells are preferably substantially greater than those of the above-described known prior pads to better accommodate higher air velocities.